After months of tough talk, House Republicans ran away from defense cuts last week –and that spells more trouble now for deficit reduction talks at the White House, already beset by differences over taxes.

In three days of floor debate, even modest reductions at the expense of military bands or the Pentagon’s sponsorship of NASCAR races to promote recruitment were opposed by the majority of GOP lawmakers. And the $649.2 billion appropriations bill, including $118.6 billion for wars overseas, sailed through Friday with only a dozen Republicans in opposition.

When conservative freshman Rep. Mick Mulvaney of South Carolina proposed to freeze core Pentagon spending at 2011 levels, he was run over by almost three-quarters of his party. A bipartisan compromise, which would have preserved an $8.5 billion increase, fared no better, getting just 47 Republicans — less than half the number that voted to wipe out the entire

“The military budget is not on the table,” said a frustrated Rep. Barney Frank (D-Mass.). “The military is at the table, and it is eating everybody else’s lunch.”

As White House talks resumed Sunday night, last week’s floor debate was a warning, too, for Republican leaders trying to reach agreement on an estimated $2.4 trillion, 10-year deficit-reduction package prior to an Aug. 2 deadline, when the federal debt ceiling must be raised.

Hopes of a much larger $4 trillion package were dashed over the weekend, as Speaker John Boehner (R-Ohio) pulled back Saturday night from a proposed deal with the White House. But as the target shrinks, defense spending cuts become more important because discretionary appropriations account for such a large proportion of the remaining savings.

Indeed, of the $1.7 trillion to $2 trillion savings already identified, more than half or $1.1 trillion is attributed to tighter limits on annual appropriations. This has set off alarms among Democrats, who want some firewall established to ensure that not all the cuts fall on domestic programs. But Republican leaders have resisted, preferring to gloss over the details for fear of setting off a revolt among pro-defense forces in their own caucuses.

House Majority Leader Eric Cantor (R-Va.) will argue that between the Democrats’ power in the Senate and Obama’s veto pen, they have nothing to fear. But last week’s House debate gave no reason for comfort. And though Cantor denies it, many believe that it was the defense issue — not just taxes — that led him to walk out last month from deficit talks led by Vice President Joe Biden.

Pro-defense lawmakers, including old friends of Boehner’s, are a key part of the House Republican Conference, and this plainly influenced the bargaining in April to avert a government shutdown. In fact, the administration played on this vulnerability by threatening defense cuts as a way to gain leverage with the speaker and House Appropriations Committee leadership and win more flexibility on domestic savings.

In the case of the Senate, Minority Whip Jon Kyl (R-Ariz.), who also participated in the Biden talks, is a strong defense advocate. And even at last Thursday’s White House meeting with Obama, Kyl pushed back against administration demands for deeper cuts from the military.

Yet here the Republican finds himself matched against Senate Appropriations Committee Chairman Daniel Inouye (D-Hawaii), who has impeccable defense credentials, earning the Medal of Honor for his combat service in World War II and spending decades overseeing the military budget.

Numbers compiled by the professional staff on Inouye’s committee show that over the past decade, the annual Pentagon appropriations bill has grown at five times the rate of domestic nonsecurity spending bills. If additional emergency war funding related to Iraq and now Afghanistan is counted, the disparity is closer to 9-to-1.

The House defense appropriations bill last week continues this trend. Core Pentagon spending would grow by $17 billion in 2012, even as the 11 remaining annual bills would be reduced about $45 billion altogether. This is in line with the Republicans’ 10-year budget, which seeks to roll back domestic appropriations to a point where, in 2021, these programs would account for a lower share of gross domestic product than during the Dwight Eisenhower administration a half-century ago.

“Personally, I like to think I am serious about cutting our deficits,” Mulvaney said of his proposal to freeze defense. “Many of us have gone around back home and told people how serious we are. But how can we look them in the eye and tell them that we are serious about cutting this deficit and about cutting spending and then come in and plus-up the base defense budget?”

“It’s easy to cut things we don’t like. It’s hard to cut things that are important to us.”

“We had hoped for better,” John Isaacs, executive director of the Council for a Livable World, told POLITICO. He took heart that 69 Republicans altogether voted for one of the two major budget-cutting amendments: the Mulvaney freeze or the Frank bipartisan alternative that preserved half of the $17 billion increase recommended by the House Appropriations leadership.

“You have scores of Republicans willing to cut defense that wouldn’t have done it just six or eight months ago,” said Rep. Jeff Flake (R-Ariz.). “Republicans think we have to have some votes on defense in order to be taken seriously on the other stuff.”

But that raises the question: Are conservatives looking to burnish their record on deficits or have real results?

Isaac faults Democrats for not taking better advantage of the Republican defectors, but critics would argue that it is hard to take serious a movement where the high-water mark on defense cuts was just 90 Republicans willing to reduce funding for military bands.

Mulvaney’s freeze, which never had a chance, got 18 more Republican votes than Frank’s $8.5 billion increase, which got a total of 181 votes. If those same 18 had backed the Frank compromise, it would have been in serious contention and surely forced more Democrats to join.